Unmetaing strip cancels cuts
That's normal, meta strips always keep the content as it is.

If you want to cut both audio and video at the same time, you can use the select linked time mode to select them both. It only works if the audio and the video strips are the same length. If they aren't, just cut the extra footage on the longer strip, and it'll work. By default, it's done by pressing Ctrl + Select Mouse (Ctrl Right Click). 

Then you just have to cut like usual.



This keymap item can be found under Sequencer / Sequencer (Global)